Process for the manufacture of phthalimide



Patented Mai". 25, @241 sit JARTHUR GEORGE GREEN AND STANLEY JG$EPH GREEN, ill? MANCHESTER, ENGLAND, AB-SIGNTORS T0 BRITISH DYESTUEFS {JDEZPORATIGN LIMITED, 0F MANCHESTER,

ENGLAND.

lto Drawing. Application filed July 3,

To all whom it may concern:

Be it known that we, ARTHUR GEORGE GREEN and STANLEY J osnrrr GREEN, both residing at Blaokley, Manchester, in the county of Lancashire, England, both subiectsof the King of Great Britain and Ireland, have invented certain new and useful improvements in Processes for the Manufacture of Phthalimide, of which the following is a specification. I

It is Well lemown that whilst naphthalene produces phthalic acid upon oxidation with chromic acid the alphanitro derivative of naphthalene gives rise to nitro-phthalic acid with production of little or no phthalic acid (Beilstein and Kurbatow, Ann. 1880 (202) 218). Thus the ring to which the nitro group is attached resists the attack of the oxidizing agent.

We have found that alpha-nitronaphthalene can be directly oxidized b eans of air or oxygen in the presence 0i a suitable cata lyst or oxygen carrier and have made the remarkable obseryation that the main prodnot of this catalytic oxidation is phthalimide and no nitrophthalic acid is produced. In this case, therefore, it is the ring to which the nitro group is attached which suffers oxidation whilst the nitro group contributes a portion of the oxygen required and is itself reduced to the imide group.

lj Ve have used hitherto as catalysts or oxygencarriers an oxide of vanadium or an oxide of molybdenum but we do not restrict ourselves to the use of these specific suhstances. The yield of'phthalimide is a satisfactory one and the process, therefore, constitutes a convenient and economical method for the manufacture of this compound.

Temperatures ranging from 300 to 400 C. have hitherto proved to be the most suitable, but higher temperatures may be employed.

The following'example' will serve to illustrate further the nature of. the invention and the manner in which it can be carried into i'actical effect, but the invention is not conedfto the example. 1

.EwampZe. -A stream of hot air, in large excess of that theoretically; required, is

1922. Serial l lo. 572,724.

passed over nitroiiaphthalene heated to a temperature of 120-13() C., and thence through an iron tube containing the catalyst heated to a temperature of 320370 C. The catalyst may be prepared by adding a solution of 150 parts of ammonium vanadate in boiling water to 750 parts of pumice stone in small. lumps and evaporating the whole to dryness whilst stirring. The impregnated pumice is transferred to the re action tube and heated at 250300 C. in a current of air for several hours. The passage of the nitronaphthalene vapour is then conunenced, the products of the reaction being conducted into a large well-cooled receiver, where the phthalimide is deposited in small colourless crystals. When purified by recrystallization from hot water it forms needles of melting point 229 C. The yield of phthalirnide is upwards of per cent of that theoretically possible. A little phthalic anhydride is formed at the same time but as this is more volatile than phthal'imide it does not condense so readily but passes forward and may be collected in a second re ceiver.

What we claim and desire to secure by Letters Patent is 1. The process of manufacturing phthalimide by catalytic oxidation of oc-nitro-naphthalenc.

9.. Process of manufacturing phthalimide b oxidizii'w a-nitro-na )hthalene directl by means of oxygen in the presence of an" oxide of vanadium as catalyst.

4. Process o't manui'acturing phthalimide by dii cctly oxidizing wnitro-naphthalene by means of hot air in the presence of oxide of vanadium as catalyst.

In testimon whereof we have si ned our names to this specification.

ARTHUR GEORGE GREEN. STANLEY JOSEPH GREEN. 

